CROSS REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of priority under 35 U.S.C. § 119 of German
Patent Application DE 20 2005 011 686.6 filed Jul. 26, 2005, the entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention pertains to a compressed cartridge heater with at least one heating coil, which is arranged exposed in a metallic tubular body and is embedded in a granulated insulating material and whose ends are provided with terminals projecting from the tubular body.
BACKGROUND OF THE INVENTION
A compressed cartridge heater of this type is known, for example, from DE 70 31 974 U. A plurality of heating conductor coils with different wire thicknesses and different coil diameters are accommodated in this cartridge heater concentrically with one another, exposed in a cylindrical cartridge housing, which has a fixed front-side bottom at one end and whose other end is closed by a metal disk with wart-like holes. Instead of the otherwise usual terminal screws, strands provided with insulating jackets are connected to the ends of the heating conductors. These strands are led through the metal disk toward the inside with their insulating jackets, so that there is an insulation between the metal disk and the conductor wires of the strands.
DE 197 16 010 C1 discloses an electric jacket tube heater with integrated temperature sensor, in which the heating conductor coils are installed in a hairpin-like pattern in the jacket tube and the connection of the heating conductor is led out at one end of the jacket tube and of the connection temperature sensor at the other end of the jacket tube. The heating coil is embedded in compressed insulating material.
No support elements, which ensure that when the insulating granular material is filled in, the windings of the heating coil will not come into contact with the tube wall, are provided whatsoever for the heating coils within the metal tube in these prior-art cartridge heaters. It must rather be ensured when the granular material is filled in that the heating coils will not be bent out and are kept away in space from the tube jacket.
This makes it difficult to fill in the granular material and causes high manufacturing costs.
SUMMARY OF THE INVENTION
The basic object of the present invention is to create a compressed cartridge heater of the type mentioned in the introduction, which can be manufactured with minimal effort in terms of labor and material.
This object is accomplished according to the present invention by providing as the carrier for the heating coils a flat insulating plate, which is coordinated in its width with the internal diameter of the tubular body, wherein the heating coils extend along the two flat sides of the insulating plate and are connected to one another by a coil section that is led around a deflecting edge of the insulating plate.
Due to the arrangement according to the present invention and the provision of flat insulating plates as the carrier for the heating coil, it is substantially simpler to place heating coils within the tube such that they cannot come into contact with the wall of the tube, so that less care is needed when filling in the insulating granular material, and this filling in can be carried out substantially more rapidly and thus at a lower cost. The connecting coil section may consist of a short wire section or comprise one or more windings.
It is simplest to use the lower, narrow-side end edge of the insulating plate as the deflecting edge.
Another simple possibility of insulating the coil section led around this lower end edge against the bottom of the tubular body and of keeping it away from it is the deflecting edge being formed by the narrow-side end edge of the insulating plate and the coil section led around same being separated from the bottom of the tubular body by an insulating disk or a spacer ring.
Other advantageous possibilities of keeping the deflecting edge or the coil section led around it away from the bottom of the tubular body are presented herein.
Holding clamps may be provided that are distributed over the length of the heating coils, consist of insulating material, surround the said heating coils and are fastened at the longitudinal edges of the said insulating plate.
The holding clamps may be provided with clamping fingers, which mesh with said locking notches of the insulating plate. The holding clamps may comprise U-shaped flat bodies and have U-shaped recesses in which the heating coils (8, 9) are guided. These measures guarantee simple and reliable fastening of the holding clamps on the insulating plate and, moreover, sufficient fixation in space of the heating coils within the tubular body.
To also have the possibility of arranging two heating coils on each flat side of the insulating plate, the heating coils may be connected to one another in pairs that can be associated with different heating circuits on the two flat sides of the insulating plate.
Another advantageous embodiment of the cartridge heater according to the present invention presents the special advantages that the heating coils extending in parallel next to one another are mutually insulated by the insulating plates located in between.
Several possibilities of embodiment are available for designing the insulating plates.
Holding clamps, which prevent the individual heating coil strands from bending out radially, may be provided in case of greater overall length.
The present invention will be explained in greater detail below on the basis of the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a side view of a compressed cartridge heater;
FIG. 2 is a top view II from FIG. 1;
FIG. 3 is a section III from FIG. 2;
FIG. 3 a is a sectional view of the lower section of the cartridge heater with another insulating plate;
FIG. 4 is a 3-D view of the cartridge heater with a cut-away sectioned tubular body;
FIG. 5 is a perspective showing an insulating plate as an individual part;
FIG. 5 a is another embodiment of the insulating plate from FIG. 5;
FIG. 6 is a holding clamp as an individual part;
FIG. 7 is an isometric view of a carrier plate with two heating coil pairs;
FIG. 7 a an isometric view showing a variant of FIG. 7;
FIG. 8 is a front view VIII from FIG. 7 with the tubular body from FIG. 4;
FIG. 9 is a perspective view showing the holding clamps from FIG. 7 as individual parts;
FIG. 10 is an isometric side view of another cartridge heater;
FIG. 11 is a front view XI from FIG. 10;
FIG. 12 is an isometric view of the carrier plates and heating coils arranged in the tubular body according to FIGS. 10 and 11;
FIG. 13 is a perspective view showing the two insulating plates according to FIG. 12 as individual parts;
FIG. 14 is a perspective view showing the closing disk from FIG. 10 as an individual part;
FIG. 14 a is a perspective view showing a variant of the closing disk of FIG. 14;
FIG. 15 is a perspective view showing the holding clamps from FIG. 12 as individual parts;
FIG. 16 is an isometric view of another embodiment of the intersecting insulating plates as individual parts;
FIG. 17 a perspective view showing the insulating plates from FIG. 16 in the assembled state;
FIG. 18 is a partially cut-away, isometric view of insulating plates that are assembled according to the principle of FIGS. 16 and 17, but which have no recesses at the lower edge;
FIG. 18 a is a sectional view of the lower section of the cartridge heater in the embodiment according to FIG. 18;
FIG. 19 is partially cut-away, isometric view showing a variant of the embodiment according to FIG. 18;
FIG. 20 is partially cut-away, isometric view showing a variant of the embodiment according to FIG. 18;
FIG. 20 a is a perspective view showing the insulating plates according to FIG. 20 as individual parts; and
FIG. 20 b of the lower section of the cartridge heater in the embodiment according to FIG. 20.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings in particular, the
cartridge heater 1 comprises a cylindrical
tubular body 2, which has a
fixed bottom 3 and whose upper, open end
4 is closed by a
closing disk 5. The
tubular body 2 consists of metal, preferably stainless steel. It may also consist of brass, copper or the like.
The
closing disk 5 consists of an insulating material and is provided with
passage openings 6 for
terminal screws 7 of two
heating coils 8 and
9. The two
heating coils 8 and
9 extend on both sides of an insulating
plate 10, which is arranged centrally in the
tubular body 2 and acts as a carrier for the heating coils
8 and
9.
In the embodiment according to
FIGS. 1 through 3 as well as
FIGS. 4 and 5, the insulating
plate 10 is provided, in the area of its lower end, with a
recess 11 shaped as a hole, through which a
coil section 12 connecting the two
heating coils 8 and
9 to one another is led. As is shown in
FIGS. 7 through 13, the recess may also be designed as an
open slot 11′. The deflecting edge, with which the
coil section 12 is in contact, is located in the
recess 11 or
11′ in these embodiments.
These
recesses 11 and
11′ expediently have a size coordinated with the diameter of the heating coils
8 and
9, so that one of the two
heating coils 8,
9 can be easily lead through this
recess 11 or
11′.
As is shown in
FIG. 3 a, it is also possible to use the
lower end edge 27 of the insulating
plate 10 as a deflecting edge and to lead the connecting
coil section 12 directly around this
end edge 27. However, it is necessary for this to insulate the
coil section 12 by an inserted insulating
disk 26 against the
bottom 3. To achieve a certain fixation of the position for the
coil section 12 in this case as well, the lower end edge of the insulating
plate 10 may be provided with a notch, not shown. The notch is used as a deflecting edge for the
coil section 12 in this embodiment.
As is shown by the example according to
FIGS. 18 through 20 b, it is also possible to establish an insulating distance from the
bottom 3 by inserting a
spacer ring 40 made of an insulating material, e.g., ceramic, on which the lower edge of the insulating
plate 10 is seated.
The cavity of the
tubular body 2 between the bottom
3 and the
closing disk 5 is filled with an insulating material (granulated insulating material)
13, which may consist of quartz sand or a metal oxide, especially magnesium oxide. A granular product consisting of heat-resistant plastic may also be used for this purpose.
It shall be pointed out here that the drawings show the
cartridge heater 1 in the noncompressed state.
In case of relatively small overall lengths of the
tubular body 2, the two
heating coils 8 and
9 are sufficiently guided within the
tubular body 2 by the insulating
plate 10 and the two
terminal screws 7, which are rigidly connected to the upper ends of the heating coils
8 and
9, and are protected against bending out radially and thus against touching the wall of the tubular body.
If the cartridge heater has a greater overall length, it is useful to secure the heating coils
8 and
9 by holding
clamps 14 arranged distributed over the length. These holding clamps
14 consist of U-shaped flat bodies made of insulating material and are provided with
U-shaped recesses 15, in which the heating coils
8 and
9 are guided.
In addition, these holding clamps have clamping
fingers 16 and
17, which engage locking
notches 18 of the insulating
plate 10 in a locking and positive-locking manner. These locking
notches 18 are arranged in pairs opposite each other on the
longitudinal edges 19 and
20 of the insulating
plate 10. With support surfaces
21 arranged on both sides of the
U-shaped recess 15, the holding clamps
14 are in contact with the respective flat sides of the insulating
plate 10. The insulating
plate 10 may consist of micanite or ceramic or plastic.
Two
heating coils 8 and
8′ and
9 and
9′ each are arranged on both sides of the insulating
plate 10 in such a way that they extend in parallel to one another in the embodiment according to
FIGS. 7 and 8. Their top ends are connected to the respective
terminal screws 7 and
7′. The two
heating coils 8 and
8′ are visible in
FIG. 8 only.
The insulating
plate 10 is provided with two slot-
like recesses 11′ at its lower end in this embodiment. These recesses could also be designed as holes.
To also support the two
heating coils 8 and
8′ on one side and
9 and
9′ on the other side of the insulating
plate 10 against bending out at the same time, holding clamps
14′, which are arranged distributed over the length, are equipped with two
U-shaped recesses 15′ each, and by which a
heating coil 8,
8′ and
9,
9′ each is guided, are provided.
These holding clamps
14′ are also provided with
lateral clamping fingers 16 and
17, which engage
notches 18 of the insulating
plate 10 in a positive-locking manner. Between the
U-shaped recesses 15 and
15′, there is a
support finger 22, whose
front surface 21 with the other two
support surfaces 21 at the clamping
fingers 17 and
18 is supportingly in contact with the flat side of the insulating
plate 10.
In the embodiment according to
FIGS. 7 and 8, a
closing disk 5′ (
FIG. 14) with four
passage openings 6 is provided, through which the four
terminal screws 7 and
7′ are led to the outside.
The embodiment according to
FIG. 7 a provides for the
terminal screws 7′ of the two
heating coils 9 and
9′ (
FIG. 8) to be arranged at the lower end of the insulating
plate 10 and thus to project from the
tubular body 2 on the lower front side. Accordingly, the
tubular body 2 is not equipped with a lower
front wall 3 but, instead, likewise with a
closing disk 5″ according to
FIG. 14 a, which is also used to close the upper end of the tubular body in this case. The
passage openings 6 of this
closing disk 5″ are arranged, corresponding to the
terminal screws 7 and
7′, eccentrically, offset to one side in relation to the
central plane 25.
In the embodiment according to
FIGS. 10 through 15, the cavity of the
tubular body 2 is divided by two insulating
plates 10′, which intersect centrally, into four
space sectors 31,
32,
33 and
34 (
FIG. 11), in which a
heating coil 8,
8′,
9,
9′ each is located. At least one of the insulating
plates 10′ must be provided with two
recesses 11, through which a
coil section 12 each extends, which connects two
heating coils 8 and
8′ as well as
9 and
9′ extending on the two flat sides of the insulating
plate 10′ to one another.
In the exemplary embodiment according to
FIG. 13, both insulating
plates 10′ are provided with two slot-
like recesses 11′ each at both the top end and the lower end, so that these two can be pushed into the
tubular body 2 in any desired position in a centrally crossing position, as is shown in
FIGS. 11 and 12. Strictly speaking, this is only an insulating
plate 10′ that is present in a pair, one of which is upside down. To make it possible to connect the two insulating
plates 10′ to one another in a crossing position in a positive-locking manner, the two insulating
plates 10′ are provided with
insertion slots 35 each, which extend centrally and symmetrically to their
longitudinal axis 35. These
insertion slots 35 have a width b
1 each, which corresponds to the thickness d of an insulating
plate 10′. To make it possible to insert flush the two insulating
plates 10′, which are of equal length and equal width and are also shaped identically otherwise, it is necessary for these
insertion slots 35 to extend at least over half the length s.
These insulating
plates 10′ are also provided with
open slots 11′ (
FIG. 5 a) instead of with
holes 11.
To support the heating coils
8,
8′,
9 and
9′, holding clamps
14″ made of insulating material, which have a U-shaped flat shape, are provided with two clamping
fingers 16 and
17 and also have support surfaces
21. The
recesses 15 and
15′, which are designed without
support fingers 22 in this case, are located between the support surfaces. A notch-
like recess 15/
1, whose
connection web 15/
2 is accommodated by a
notch 18 of the respective bridged-over insulating
plate 10′ is provided between these
recesses 15 and
15′.
The holding clamps 14″ are otherwise used in the same manner as the holding clamps 14′.
Other embodiments of insulating plates arranged crosswise are shown in
FIGS. 16 through 20 b. A first insulating
plate 10/
1 of the usual shape and with the locking
notches 18 arranged at the
longitudinal edges 19 and
20 is provided for fastening holding clamps
14″ according to
FIGS. 12 and 15.
This insulating
plate 10/
1 has
insertion slots 35′ each, extending symmetrically to its
longitudinal axis 36, in the area of its narrow-side end sections. These two
insertion slots 35′ have a width b
2, which corresponds to twice the thickness d second insulating
plate 10/
2. In addition, these
insertion slots 35′ have a longitudinal distance s
1. This longitudinal distance s
1 corresponds to the length s
1 of a
rectangular opening 35/
1, which the two second insulating
plates 10/
2, which otherwise have an identical shape, have. The two remaining
end sections 42 of these two second insulating
plates 10/
2 have the width b.
The width b
3 of the
openings 35/
1 corresponds to b/
2+d/
2. As a result, as is shown in
FIG. 17, the
end sections 42 can be introduced congruently into the
insertion slots 35′ of the insulating
plate 10/
1 such that they project from these by equal amounts on both sides.
The upper and
lower end sections 42 of the two second insulating
plates 10/
2 touch each other on their flat sides, as is shown in
FIG. 17. The outer edges
20 of the second insulating
plates 10/
2 are likewise provided with locking
notches 18, which are used to receive holding
clamps 14′ (
FIG. 15).
The upper and
lower end sections 42 of the second insulating
plates 10/
2 are provided each with recesses
11′, which are arranged symmetrically to the first insulating
plate 10/
1 and are mutually flush with one another and through which
coil sections 12 or
windings 12′ of the heating coils
8,
9 can be led.
To make it possible to do away with
such recesses 11′ and to use the lower, closed end edges
27 as deflecting edges for the
coil section 12 or
windings 12′, a
spacer ring 40 each, which is seated on the
bottom 3 and at the
top edge 41 of which the insulating
plates 10/
1 and
10/
2 are seated, is provided in the embodiments according to
FIGS. 18 through 20 b. As a result, the
coil section 12 or the
windings 12′ receive the proper distance from the
bottom 3 of the
tubular body 2.
In the embodiment according to
FIGS. 19 and 20, the first insulating
plate 10/
1 is provided with an
extension 43 protruding into the
spacer ring 40. The
insertion slot 35′ is not led up to the lower end of this
extension 43 in this embodiment, but it rather ends at the level of a
support shoulder 44, with which the first insulating
plate 10/
1 is seated on the
upper edge 41 of the
spacer ring 40.
This
extension 43 is also present in the embodiment according to
FIG. 18 a. The two
heating coils 8 and
9, which are connected to one another in one piece, are led around the
lower edges 27 of the two second insulating
plates 10/
2 with a plurality of
windings 12′, which are shown in
exemplary embodiment 3. The
extension 43 of the first insulating
plate 10/
1 protects the
windings 12′ of the heating coils
8 and
9 extending on the two sides of the insulating
plate 10/
1, which said
windings 12′ are led around the
lower edges 27 of the second insulating
plates 10/
2, against mutually touching one another.
In
FIGS. 20,
20 a and
20 b, the two second insulating
plates 10/
2 are provided with an
extension 43′ each, which is arranged between two
recesses 45, which are open on the side and at the end.
The deflecting edges are formed by the
horizontal sections 46 of the
recesses 45 in this embodiment. As can be recognized from
FIG. 20, a plurality of
windings 12′ of the heating coils
8 and
9 can be led around these deflecting
edges 46 and maintain the necessary distance from the bottom
3 in the case of the
recesses 45 that are open both on the end and laterally.
The cartridge heater is assembled in all embodiments shown such that the heating coils
8,
8′,
9,
9′ are first mounted with the respective
terminal screws 7 and
7′ fastened thereto on the insulating
plates 10 and
10′ in the manner shown in the drawing and are secured by the holding clamps
14 and
14′ or
14″. This premounted component is then inserted into the
tubular body 2 and the remaining cavity is filled with the granulated insulating material from the open upper side. The
closing disk 5 and
5′ is then inserted into the upper end of the
tubular body 2 and the tubular body is pressed radially from the outside such that not only does the granulated insulating material undergo intense compaction, but the
passage openings 6 of the
closing disk 5 and
5′ are also reduced in size such that they are tightly in contact with the
terminal screws 7 and
7′.
Instead of the usual
terminal screws 7,
7′, it is also possible to provide other terminals, as is known from DE 70 31 974 U, e.g., jacketed strands.
The
closing disks 5,
5′ and
5″ consisting of insulating solids may also be replaced with other closing means. Depending on the nature of the insulating material filled into the tubular body, they may even be able to be omitted.
It is easy to imagine that the heating coils
8,
8′,
9,
9′ fastened to the insulating plate or
plates 10 and
10′ do not run the risk of coming into contact with the wall of the
tubular body 2, especially because they are also secured by the holding clamps
14 and
14′ and
14″ against bending out radially. Since this granulated insulating material is a very fine-grained material, which has a high flowability, the filling into the tubular body can be carried out in a relatively problem-free manner such that no cavities, which can be reliably prevented from occurring by simple vibration, are left.
On the whole, the assembly of the heating coils
8 through
9′ and the filling in of the granulated insulating material are substantially simplified and thus also made less expensive by the use of the insulating
plates 10 and
10′.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.